PROJECT SUMMARY Persons with serious mental illness (SMI) die on average 10-15 years earlier than those in the general population. Smoking is the strongest risk factor for their elevated mortality. Helping SMI smokers to quit is an urgent and unmet need. The hospital is an optimal setting to provide smoking cessation services. Hospital admissions for SMI are common with more than 1.2 million inpatient stays for schizophrenia and mood disorders per year in the US. Hospitalized patients experience required abstinence, are available for counseling, and can try cessation medications in a supportive setting. The challenge is how to engage SMI patients in cessation services post-discharge. An easy-to-access digital intervention is a scalable and sustainable way to bridge the inpatient-to-outpatient gap and to promote sustained abstinence. Digital interventions can deliver all elements of cessation treatment and yield quit rates comparable to face to face and telephonic interventions. SMI patients use and benefit from technology-based interventions but currently there is no digital smoking cessation program addressing their needs. This R34 application will adapt a proven digital intervention, BecomeAnEX (EX), developed and run by Truth Initiative for over 10 years. Its core components are real- time one on one coaching via live chat, nicotine replacement therapy decision support and delivery, personalized quit plans, a large online social network for peer support, a robust and fully integrated text message program, and tailored email messaging. Adaptation will ensure that EX addresses the specific challenges of SMI smokers and is in line with principles of mental health recovery. In Aim 1 we will develop and obtain preliminary feedback about EX-SMI, a version of EX adapted for SMI patients. A priori target mechanisms are motivation, abstinence self-efficacy, and cravings. In Aim 2 we will conduct a one-arm pilot trial and obtain feedback from 20 SMI smokers recruited during psychiatric hospitalization and followed up at 2-weeks and 1-month post-discharge. Feasibility and acceptability will be assessed via participant feedback regarding their intervention experience, changes in motivation, self-efficacy and cravings, and automated tracking data on EX-SMI use post-discharge. In Aim 3, 90 SMI smokers recruited during psychiatric hospitalization will be randomized to usual care or to a revised version of EX-SMI and followed for 3 months after the hospital stay. We will compare the feasibility/acceptability of EX-SMI, measure intervention impact on target mechanisms, and obtain initial estimates of efficacy on 7-day point prevalence abstinence. This pilot work directly addresses priorities of this RFA in refining and optimizing an efficacious intervention for a new target population. Ultimately, this program of research could have a powerful public health impact by increasing smoking cessation among persons with SMI.